M18x R2 USB 3.1 Speeds

I recently bought the Sandisk Extreme Pro 3.1 128GB USB, ofc first thing i did when it arrived was check the promised speeds, to see if they match the advertised...

To my dissapointment i found that the USB barely reaches 250MB/s read/write speeds.
Advertised: 420MB/s read & 380MB/s write.
I tested on all four ports and the result was the same.
I even tested it with the E6530, no dice.

I am thinking Ivy Bridge might have some limitation or i got a lemon? (Feels like running S3 SSD on S2...

M18x R2 USB 3.1 Speeds

M18x R2 USB 3.1 Speeds